With CSS it is possible to have the content of the page load before the structure -- navigation, menus, etc. -- even though the structure is displayed at the top of the page. This provides a nicer experience to text browsers like Lynx, or any surfer which avoids rodents, since one doesn't have to tab through redundant links before getting to the meat of the page. I imagine the same holds true for text-to-speech browsers.

There are fourteen structural links at the beginning of this page. To see them in all their gory detail in Mozilla, use Ctrl-I . To experience them slap tab a dozen times.

Currently, content-before-structure works but only until you put a % TOC% block in the page, then you have a great big list o' links at the top of the page again.
(Example)
You can't put a div TOC block in the template, because it get's read before the page contents do, and thus there is no TOC yet.

http://alistapart.com/articles/negativemargins/ - "Creating Liquid Layouts with Negative Margins" by Ryan Brill: a two-column liquid layout with a header and footer in which the content needed to come before the sidebar in the source code.